Tankers

ABSTRACT

884,718. Carrying liquefied gases. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N. V. Dec. 14, 1959 [Dec. 16, 1958], No. 42406/59. Class 113. [Also in Group XXVIII] In a tanker for transporting liquefied gases at atmospheric pressure having holds 5 with walls 3 integral with the tanker&#39;s structure I, at least one hold is internally provided with loadbearing heat-insulating material 7 supporting at substantially all points under all temperature conditions a thin-walled flexible container 8 of a material resistant to low temperatures, e.g. stainless steel. The container has at least one bellows-shaped part 9 parallel to a vertical diaginal plane of the container and is provided with means 14, 15 for prestressing the bellows. The top of the container is protected by flexible heat-insulation 18 e.g. foamed glass. The insulation 7 comprises balsa wood 20, Fig. 6, secured to the container 8, layers of foamed glass 21, perlite concrete 22 and cork 23. To prevent the ingress of humid air and in formation, a dry inert gas such as nitrogen is supplied to the insulation through pipes 24. The spaces 28 around the holds may be filled with a liquid, e.g. oil, with means for heating same.

June 19, 1962 R. VERSLLHS 3,039,418

TANKERS Filed Nov. 50, 1959 5 Sheets-Sheet 1 i"gj; O n O o @@QQOOOO@mvENToR R01-:LAND VERSLUIS BY MD. @Mc/'L HIS ATTORNEY June 19, 1962 R.VERSLUIS 3,039,418

TANKERS Filed NOV. 50, 1959 3 Sheets-Sheet 2 INVENToR ROELAND VERSLUISBY D. @Miva HIS ATTORNEY June 19, 1962 R. VERSLUIS 3,039,418

TANxERs Filed Nov. 30, 1959 5 Sheets-Sheet 3 INVENTOR ROELAND VERSLUISBY f4 D, 13M@ HIS ATTORNEY United Sttes 3,039,418 Patented June 19, 1962Free 3,039,418 TANKERS Roeland Versluis, The Hague, Netherlands,assignor to Shell Oil Company, a corporation of Delaware Filed Nov. 30,1959, Ser. No. 856,243 Claims priority, application Netherlands Dec. 16,1958 1 Claim. (Cl. 114 74) The invention relates to a tanker suitablefor the transport of liquefied gases, at atmospheric or substantiallyatmospheric pressure, which tanker is provided with holds of which thewalls are integral with the ships structure.

The object of the invention is to provide a tanker suitable for thetransport of liquefied gases, such as methane, propane, butane ormixtures thereof, at atmospheric or substantially atmospheric pressure.Since the temperature of these liquefied gases at the said pressure isvery low (in the case of methane 160 C.) the ships structure should beof a very special standard as shipbuilding steel should not be exposedto very low temperatures which would reduce the strength of the shipsstructure to an inadmissably low value. Good heat insulation istherefore required to prevent transmission of the low temperature to theships structure. The liquefied gas must be stored in tanks or containerscapable of resisting the low temperatures occurring. In addition, theweight of the liquid in the tanks or containers and the forces generatedby the liquid lapping to and fro must be transmitted to the shipsstructure in such a way as to ensure the best possible distribution.

According to the invention, the said tanker is therefore characterizedin that at least one hold is internally provided with a layer ofload-bearing, heat-insulating material, this layer supporting athin-walled container made of a metal resistant to low temperatures,which container is so flexible and has such dimensions that, under alltemperature conditions anticipated, its walls are supported by theinsulating layer in all points.

The container should be constructed of a metal which is resistant to lowtemperatures, i.e. a metal which retains adequate ductility and strengthat the low temperatures concerned. A suitable metal is, for instance, alow carbon steel having 18% chromium content and 8% nickel contentcommonly known as 18/8 stainless steel, but other metals possessing theabove properties may also be used. The thickness of the -wall of thecontainer should be of the order of about 8 mm. It will be understoodthat by thin-walled container is meant a container of which the wallthickness is approximately that specified above.

In order to give the container the required exibility, its walls may beprovided with at least one bellowsshaped part. This bellows-shaped partshould be located' in such a way that the overall size of the containerremains substantially the same in overall dimensions rcgardless ofchanges in temperature.

Provided the bellows-shaped part is properly located only one is neededper container. When using a rectangular container this end is suitablyattained by positioning the bellows-shaped part parallel to a verticaldiagonal plane of the container.

Means are preferably present for prestressing the bellows-shaped part ofthe container. This has the advantage that they enable the bellows to beprestressed at normal ambient temperature. The insulating material maythen be arranged between the walls of the holds and' the walls of thecontainer. The prestress may subsequently be reduced to zero and thecontainer filled with the liquefied gas. Its low temperature will causethe container to contract and when the dimensions are accurate, theentire surface of the latter will be in contact with the insulatingmaterial and be supported thereby in such a manner as to exert thecorrect pressure. The correct pressure at which the walls of thecontainer .are in Contact with the insulating material is obtained by soprestressing the bellows-shaped part at the normal ambient temperatureas to reduce the overall dimensions of the container by a value equal tothe decrease in the overall dimensions of the container which resultsfrom cooling by the cold liquid introduced into the container. Theheat-insulating lining of the hold should be capable of absorbing theweight of the container filled with liquid and also the forces generatedby the liquid lapping to and fro and of transmitting them to the shipsstructure. `On the other hand, the insulating lining should havesufficient flexibility to make allowance for movements in the shipsstructure. insulating lining to contain a gas-tight layer to prevent theingress of air mixed with moisture particles, which leads to iceformation and undesirable stresses in the insulating lining. Inaddition, it is advisable to arrange a liquid-impermeable layer toprevent the liquid from flowing out, should there be leakage of liquidfrom the container. This liquid-impermeable layer should be capable ofretaining the liquid for at least 24 hours to enable the container to beemptied in time.

The heat-insulating lining therefore preferably consists of variouslayers, including flexible and gasand/ or liquid-tight layers.

In order to m-ake allowance for vertical expansion of the container itis advisable to insulate the top part of the container with a flexiblematerial such as foam-glass.

A preferred embodiment of the tanker according to the invention will nowbe described with reference to the drawing.

FIG. l is a cross-section (on the line 1 1 in FIG. 2) of the tankeraccording to the invention.

FIG. 2 is a top plan View, partly in cross-section (on the line 2 2 inFIG. l) of a portion of the tanker.

FIG. 3 is a cross-section of a container for the storage of theliquefied gas (on the line 3 3 in FIG. 2).

FIG. 4 is a cross-section of the container (on the line 4 4 in FIG. 2).

FIG. 5 is a top plan view of the entire tanker.

FIG. 6 is a cross-section of the heat-insulating layers.

Referring to the drawing, the ships skin 2 is connected to the frames 1all of which are designated by the numeral 1. Walls 3 are internallyarranged and are integral with the ships structure constituted by theframes 1. The holds 5 are thus formed. The walls 3 are internallyprovided with a load-bearing, heat-insulating material which isdiagrammatically shown as the single layer 7 in FIG. l. The layer 7supports the thin-walled flexible container 8, the wall-thickness ofwhich is of the order of about 8 mm. These walls may be constructed of18/8 stainless steel which has the advantage that it does not becomebrittle and retains its strength at low temperatures, but other metalspossessing the said properties m-ay also be used. The container 8 isprovided with a bellows-shaped part 9 which is positioned parallel to avertical diagonal plane of the container 8, as is clearly shown by FIG.2. The bellowsfshaped part 9 ensures that in normal service the entireflat surface of the walls and bottom of the container will be in contactwith and will be supported by the insulating layer 7 notwithstandingchanges intemperature The horizontal top wall 10 of the container 8 isreinforced by the beams 11, but the other walls of the container 8 arenot reinforced. The bellows-shaped part 9 is supported by stay rods 13which prevent the bellows 9 from buckling. Other rods 14 connected tothe walls It is also desirable for the of the container 8 serve toprestress bellows 9, if desired. This may be done by turning the nuts15, whereby the rods 14 move towards each other in an axial direction.

The top part of the container 8 is provided with a dome 17. This has theadvantage that the formation of waves in the tank is greatly reduced ifthe vessel 8 is lled up to such a level that the liquid rises into thedome 17.

In order to allow the container 8 to expand in a vertical direction, itis desirable for the top part of the container 8 to be covered with alayer of flexible, heatinsulating material, for instance withfoam-glass. This layer is designated by the reference numeral 18.

The insulation 7 which is secured to the walls 3 of the holds 5 may, forinstance, be designed as shown in FIG. 6.

Referring to FIG. 6, a layer of balsa wood 20 is secured to the wall ofthe container 8 and three layers of foam-glass 21 are arranged againstthis layer. The foam glass layers 21 have the advantage of providing agastight seal. An insulating layer consisting of perlite concrete isarranged against the foam-glass layers; this is denoted by the referencenumeral 22. A more or less flexible layer of cork 23 serves to absorbthe movements in the ships structure.

In order to prevent as much as possible the ingress of humid air intothe insulation, which would lead to ice formation in this insulation,pipes 24, shown in FIG. 1, are arranged for supplying to the insulationa dry inert gas such as nitrogen.

The container 8 may be lled and emptied through the line 25. The dome 17is provided with a gas outlet 26 for venting gas formed by liquidevaporated by the inflow of heat.

I claim as my invention:

A tanker for transporting liquefied gases such as methane, propane,butane and mixtures thereof at about atmospheric pressure comprising: ahull structure, holds having walls formed in said hull structure, thewalls of said holds being integral with the hull structure, a layer ofload-bearing, heat-insulating material provided on the inside of atleast one of said holds, a thin walled metal container supported by saidload-bearing heat insulating material, a bellows-shaped part forming acontinuous belt integral with the walls of said container and positionedparallel to a vertical diagonal plane of the container, said containerbeing of such dimensions and of such flexible construction that thewalls thereof are continuously supported by said layer of load-bearing,heatinsulated material under all temperature conditions anticipated.

References Cited n the file of this patent UNITED STATES PATENTS2,350,883 Duttweiler June 6, 1944 2,480,472 Jackson Aug. 30, 19492,807,143 Schnellhardt Sept. 24, 1957 2,859,895 Beckwith NOV. 11, 19582,889,953 Morrison June 9, 1959 2,896,416 Henry July 28, 1959 2,897,657Rupp Aug. 4, 1959 2,905,352 Henry Sept. 22, 1959 2,926,810 Yeager Mar.1, 1960 2,963,873 S'toWerS Dec. 13, 1960 FOREIGN PATENTS 746,567 GermanyAug. 12, 1944 1,079,634 France May 19, 1954 1,170,576 France Sept. 22,1958 1,174,820 France Nov. 10, 1958

